Facile Synthesis of 2-Amino-4,6-dimethoxypyrimidine over Lewis Acidic Ionic Liquid Catalysts

2-amino-4,6-dimethoxypyrimidine (ADMP) is an important intermediate for the synthesis of sulfonylurea herbicides. As the most critical step in the ADMP synthesis, ADMP prepared by cyclization of 3-amino-3-methoxy-N-cyano-2-propaneamidine (AMCP) are rarely reported, especially its reaction mechanism. Here, a Lewis acidic ionic liquid catalyst was firstly introduced to increase reaction rate. The Et₃NHCl-2ZnCl₂ catalyst possesses excellent catalytic performance and good stability. The yield of ADMP can reach up to 94.8% under 50 °C for 3 h. And the catalytic mechanism was studied. The anion of Et₃NHCl-2ZnCl₂ is conducive to ring formation, and the cation is conducive to hydrogen transfer during rearrangement. The stronger Lewis acidity of the catalyst is conducive to cyclization. This work firstly introduces Lewis acidic ionic liquids into the process of AMCP catalytic cyclization to ADMP, which can open novel vistas for the more economically and faster preparation for ADMP.